Stereophonic sound reproducing loudspeaker system



Sep- 24) 1963 H. F. -OLSON 3,104,729

. sTEREoPHoNIc SOUND REPRODUCING LOUDSPEAKEB SYSTEM Filed Nov. 2, 1959 '7 Sheets-Sheet l INVENTOR. l #A2/2y F.' 01.50A/

Sept. 24, 1963 H, F, OLSON 3,104,729

STEREOPHONIC SOUND REPRODUCING LOUDSPEAKER SYSTEM Filed Nov. 2, 1959 7 Sheets-Sheet 2 INVENTOR.

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STEREOPHONIC SOUND REPRODUCING LOUDSPEAKER SYSTEM Filed Nov. 2, 1959 7 Sheets-Sheet 5 isa.

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STEREOPHONIC SOUND REPRODUCING LOUDSPEAKER SYSTEM Filed Nov. 2, 1959 7 Sheets-Sheet '7 'IIN I sa 9.4/4 l I 22d 0M/" i i I l l INVENTOR. /Amy @wa/V BYMv United States Patent C 3,li,729 STEREPHONIC SGUND REPRDUCING LOUDSPEAKER SYSTEM Harry F. Olson, Princeton, NJ., assigner to Radio Cor poration of America, a corporation of Delaware Filed Nov. 2, i959, Ser. No. 850,248 17 Claims. (Cl. 181-31) The present invention relates'to a stereophonic sound reproducing loudspeaker system for use in the home entertainment field in connection with two-channel Stereophonic radio receivers, phonographs and the like.

Two-channel :stereophonic sound reproducing systems, as is known, involve the use of two stereophonically-related audio-frequency sound signals, such as may be derived from two laterallyaspaced microphones at the original sound sources of program material. These signals are translated in two separate -signal channels for stereophonic recording and/or radio broadcasting. In reproducing such twochannel stereophonically-related sound signals through .stereophonic radio receiver means, or from stereophonic phonograph records for example, the identity and stereophonic relation of the two signals is preserved through the similar use of two separate sound signal translating channels, with separate and individual sound-reproducing loudspeaker means for each channel.

A stereophonie Isound reproducing system provides for the reproduction of sound in auditory perspective. A-s is known, this gives a subjective illusion of the distribution of the sound sources reproduced by the two loudspeaker means, in lateral directions as well as depth, in a geometrical configuration which approximates the position of the original sound sources. In a two-channel stereophonic sound-reproducing system, to reproduce the stereophonic sound with the original spatial effect or in proper audio perspective, the two loudspeaker means are spaced apart and are generally located along a wall of a suitable relatively large listening area such .as a living room, in cabinets or other suitable enclosure and baffling means, facing in the same generally frontal direction.

With thi-s arrangement, the area (or volume) of the room in which sound distribution in good auditory perspective is obtained, with any presently known two-channel stereophonic sound reproducing system, is somewhat restricted. For example, the area yover which good auditory perspective is obtained with the average stereophonic radio receiver, phonograph or like system having such dual lspeaker arrangement, may represent only about onequarter of the area of the room. Thus for typical laterally-spaced loudspeaker locations at one end of a room, the distribution is such that the area of satisfactory auditory perspective occurs in and along lthe middle area. The auditory perspective along the side walls is relatively unsatisfactory. Thus, it will be seen that the sound distribution With good auditory perspective is obtained over an area which is the least satisfactory from a listening standpoint in a room. It is desirable, therefore, to provide a stereophonic loudspeaker system which develops good -auditory perspective of Ithe reproduced sound over the greater portion of the area of a room, including areas along the adjacent side walls.

The use of two separate and spaced loudspeaker cabinet units, or equivalent enclosure means, however, is often considered an undesirable feature of present known stereophonic sound reproducing systems. The main objections are the separated space requirements and the fitting of the two cabinet units to the decor of a room. 'ln some cases the problem is further complicated by the use of a third cabinet unit which includes the radio, phonograph or other related apparatus, and may .additionally provide for low-frequency sound reproduction or reinforcement from both channels. It is, therefore, desirable to provide ICC .a centralized stereophonic loudspeaker sys-tem housed in a Single cabinet or equivalent enclosure means of moderate dimensions. Many attempts have been made in this direction but Without achieving -sound distribution in full auditory perspective over a Wide and useful area. There remains, therefore, a need for an effective single-unit or unitized Stereophonic loudspeaker system of this type.

Accordingly, it is an object of this invention .-to provide an improved and unitized stereophonic loudspeaker -system for sound reproduction in :substantially uniform auditory perspective over an extended and relatively wide .area frontally thereof, from a two-channel stereophonic sound signal source.

IIt is a further object of ythis invention to provide an improved `stereophonic loudspeaker system which will cover the major portion of 4the area of a room with reproduced sound in good auditory perspective substantially uniformly therein and along the adjoining walls, and having a :single cabinet structure or unit which may also house associated sterophonic signal translating apparatus.

lt is also an object of this invention to provide a singleunit stereophonic loudspeaker system which operates to produce stereophonic sound from any two-channel stereophonic sound signal :source with good auditory perspective in a major portion of an extended and wide area of a room, frontally thereof, or toward which it is directed, and which is effectively housed and bailled in a unitized cabinet `structure or like enclosure means of moderate dimensions required for home use with radio, phonograph .and like apparatus.

To provide a wider stereophonic sound area with uniformly good auditory perspective from a stereophonic loudspeaker system, in accordance with the invention, a plurality of stereophonically-related pairs of speaker units are provided, and are located together and positioned to face in different frontal directions, at least two pairs facing slightly to the 'left and right of the center line of the system by a small angle less than Each speaker pair then faces frontally from effectively a common location or group into a resultant relatively wide listening area composed of two or more contiguous or slightly overlapping individual stereophonic sound reproducing areas or zones.

This system, therefore, involves the use of two or more pairs of loudspeaker units in a manner to provide independent sound coverage over a desired extended and Wide area which may include areas along the side Walls of a room. In other words, the loudspeaker units, from effectively .a common location or in grouped relation, are directed in pairs in different frontal directions so that each pair Will cover a certain volume or area of the total frontal volume or area to be covered.

lt has been found that only two pairs of loudspeaker units facing frontally, but angled less than 90 to the right and left of the center line of the system, may be used effectively. Also, the polar directivity lor directional patterns of the individual loudspeaker units of the stereophonic loudspeaker system may be chosen to aid in alloeating the area or zones of sound distribution of the i11- dividual pairs of speaker units. The directivity patterns, preferably, are relatively narrow and extended, so that the area of good auditory perspective for each pair of speaker units extends along fthe center line of the pair to a considerable depth. t

Further in accordance with the invention, a single or effectively unitary cabinet structure or equivalent enclosure means, of moderate and suitable dimensions for home use, is arranged in sections, which may be integral or separable in construction, to take yfull advantage of limited depth, width, and height, for the effective placement of two or more pairs of the loudspeaker units in the desired Stereophonics arrangement referred to above, and additionally to'provide for housing associated apparatus of a complete Ystereophonic sound reproducing system.

For uniformity of response and sound distribution, preferablyvlike loudspeaker units lare used. By like is meant d that the loudspeaker units are electrically and' acoustically Y alike. Thus they may have similar power-handling capacity and frequency range, and m-ay be generally, although not necessarily, of the same size, construction and impedance. v

The loudspeaker units off each pair are spaced apart in stereophonic relation in separate end sections of the enclosure means, and are connected for operation lstereol' phonically in response to applied two-channel stereoph-onicV sound signals To this end, the loudspeaker units in each end section are connected together `for operation as the left and right-channel sound reproducing elements of any FIGURE 1, showing a modication of the placement and two-channel stereophonic sound reproducing system. The

loudspeakerV system thereore has two signal inputrcircuits, one connected with the right-hand loudspeaker units as a group and the other connected with the left-hand `loudspeaker units as a group.

It may be noted that a stereophonic loudspeaker system in accordance with the invention providesv a plurality of loudspeaker units in pairs lina unitary calbinet structure, or like enclosure means, with all speaker units facing generally frontally of the structure or enclosure means, and at least two pairs of speaker units facing frontally at an acute angle to the center line or front-to-rear axis, so that none of the speaker units iface to the sides or ends of the structure or enclosure means. Stereophonic sound with better phase landl intensity factors are thereby developed over a wider frontal listening area.

The stereophonic loudspeaker system of the present invention has the additional distinct advantage in `the home entertainment field that, as referred to above, it may provide means for housing associated stereophonic sound reproducing equipment or appaartus, such as radio, phonograph, and tape playing apparatus. It has been found that the loudspeaker enclosure means or cabinet structure may be made suiciently wide, without exceeding the ylimits of moderate dimensions, to provide a central section or area which improves the spacing between the separate end sections containing the loudspeaker units, and which is d adequate Ylior housing any associated sound reproducing or other related apparatus such as the elements of a cornplete stereophonic radio, phonograph, iand/ or tape playing system. This avoids the need for any .additional means for 'enclosing associated apparatus of the above type, or low-frequencyV sound reproducing or reproducing or reenforcing loudspeaker equipment.

With this syste-m there are no separated ments for the installation and Iadapting oit a multiplicity of spaced units to the decor of a room. Instead, a single sectionalized cabinet structure or enclosure means pro vides housing iand 'bathe means for an entire stereophonic sound reproducing system which can produce stereophonic sound 'with good auditory perspective over the full width and depth of ia desired listening area. i Y

The invention, together with addi-tional objects and ad* vantages, will further be understood yfrom the following vc lescription when considered with the accompanying drawings, and its scope is pointed out in the appended claims.

In the drawings, in which like elements are designated by like reference characters throughout the various gl uvres, FIGURES l and 2 are top views, in diagram form, Y

off two stereophonic loudspeaker systems arrange/din iaccordance with the invention Vto illustrate the principles ci operation thereof;

vFIGURE 3 is a frontal view in perspective, `ot a stereophonic loudspeaker system embodying the invention, as constructediaccording; to the arrangement of FIGURE l', Vand showing the elevational relation of the speaker units;

FIGURE 4 is a plan view of the loudspeaker system shown in FdGURE 3, showing further details of consp-ace requireelevational relation of the loudspeaker units; l n

FIGURE 6 is a cross-sectional plan view of the loudspeaker system shown in FIGURE 5, taken on the section line 6 6, showing further details of construction and the angular relation of the pairs of speaker units in accordance with the invention; p

FIGURE 7 is a schematic circuit diagram oit thestereoV` phonic signal'input circuit connections for the speaker units of the system shown in FIGURES 5 and 6;

FIGURE 8 is alfrontal view in perspective, of a stereophonic loudspeaker system embodying the invention, as

Vconstructed according to the arrangement of FIGURE 2,

and showing the elevational relation of the speaker units;

FEGUIRE 9 is a cross-sectional plan view of the stereo- ,phonic loudspeaker system of FIGURE 8, taken on the section line 9 9, showing further details of construction and the angular relation of the pairs of loudspeaker units;

FIGURE l0 is a frontal view in perspective, of a stereo- Y phonic loudspeaker system embodying the invention, in the lform shown in FIGURES 8 and 9, and zas modiiied for commercial use, to provide a complete stereophonic` sound reproducing system'wi-th associated Stereophonic radio and phonograph apparatus, and

FIGURE ll is a schematic circuit diagram of the stereophouic sound reproducing system of FIGURE l0 showing the stereophonic circuit connections for the loudspeaker units with the associated stereophonic radio and phonograph apparatus.

Referring to FIGURE 1, a room, as outlined by side walls I4 and IS Vand end walls 16 and 17, is arranged for stereophonic sound reproduction with two spaced loudspeaker units LI and RI arranged along one end wall lo and connected, respectively, with a left-channel input circuit 18 and a rightchannel input circuit I9`for applying thereto two stereophonically-related sound ksignals from Iany suitable source.

As shown, the loudspeaker units face frontally in the same direction and have polar directivity patterns, shown in dash lines and indicated by the legend, which provide an elongated frontal stereophonic sound area 2d con- Viined to the center of the room and located generallyhetween boundaries represented by dotted lines ZI and 22. With a single pair of speaker units spaced apart as shown, and stereophonically operated as a single pair,'it will be seen that the area of good auditory perspective is generally along the center ofthe roomand does not include the areasalong the :side walls 14 and 15.

Since the diagrammatic representation ofthe system is a plan view, it may be Kassumed that thespeaker units Lil and Rl face frontally in the same substantially vertical plane. If the two-unit loudspeaker system, comprising the speaker units Ll and Rl, are rotated to the right or clockwise through a small angle less than while being maintained in thesame substantially vertical plane, and into a position shown as occupiedby a second pair of speaker units L2 and R2, .they still face front-ally toward the listening .area and may then provide a second stereophonic sound area 24 adjacent to first area 250, between boundaries represented by the dotted line 2l and a solid line 25. If the position ofthe speakers constituting the In `a similar manner, if the original loudspeaker system, comprising the two spaced loudspeaker units L1 and R1, is rotated to the left or counterclockwise through a similar slight angle to a position shown as occupied by a third pair of speaker units L3 and R3, the directivity pattern is'such that a third stereophonic sound area 26, having good auditory perspective, may be provided thereby between boundaries represented by the dotted line 22 and a solid line 27. This includes an area along the right wall I5 of the room and widens the area of good auditory perspective to the full width of the room if the loudspeaker units L3 and R3 are connected, as shown, respectively with the left-channel and right-channel input circuits I8 and I9.

With this arrangement, the right-hand speaker units R1, R2 and R3 are connected with the right-channel input circuit 19 and the left-hand speaker units L1, L2 and L3 are connected with the left-channel input circuit 18, whereby they operate in pairs in unison in response to applied stereophonic sound signal-s at the input circuits 22 and 23. Stereophonic sound with good auditory prespective may thus be provided over the enlarged, or extended and relatively-wide, area generally between the boundaries indicated by the lines 2S and 27. This covers a major portion of the room area frontally of the loudspeaker system.

Assuming a loudspeaker system comprising only a single pair of loudspeaker units such as L1 and R1, facing in the same frontal direction, as the sound intensity from one speaker unit is increased with respect to that from the `other unit, the sound will appear to come from the unit having the greater intensity, with respect to a listener positioned frontally of and between them, along the center line of the system.

However, if the intensity of sound from both units is the same at the listeners location and the sound from ,one is delayed there will be the illusion that the sound comes from the other speaker unit due to phase diierences in the sound which arrives from both speaker units at the listening point. Therefore, the phase and intensity of the sound from the speaker units in the listening area in stereophonic sound reproduction are important and may be determined by the angular relation of the pairs of spaced speaker units.

The directivity patterns of the individual loudspeakers of the multiple-unit stereophonic loudspeaker system shown thus serve to allocate the areas of good Stereophonic sound distribution from each individual pair `as noted herein before. For example, it will be seen that outside the central area 20 of the room, the sound delivered by a pair of spaced fully-frontally facing loudspeaker units, such as the units L1-R1, is reduced in its -stereophonic eiect, due to the discrimination introduced by the directivity characteristics of the loudspeaker units. Likewise, outside the areas 26 and 24, respectively to the right and to the left of the central area 20, the stereophonic effect of the sound delivered by the respective pairs of loudspeaker units, L- R3 and L2-R2, facing in these directions is reduced due to the discrimination introduced by the directivity characteristics of the loudspeaker units. In the vicinity of the boundaries between the three areas, represented by the dotted lines 21 and 22, the stereophonic sound will be supplied by the speaker units Ll-R1 and L2-R2 along the boundary 21, and by the speaker units Ll-Rl and L3-R3 along the boundary represented by the line 22.

From the plan view, it will be seen that the separate loudspeakers are arranged in like stereophonically-related pairs, the individual right land left-hand elements of which are eifectively arranged in two distinct spaced groups due to the shift, about a common aXis, lof the planes in which the speaker units operate. Due to this shift, furthermore, the units of the leftand rightJhand pairs ot speakers are eifectively spaced in depth from front to rear, that is, the speaker unit R3 is rearwardly d disposed with respect to its companion speaker L3, and likewise the speaker unit L2 is rearwardly disposed with respect to its companion speaker R2.

It will further be seen from the diagram or plan View, that the front-to-rear and the lateral or side-to-side spacing of the speaker units of each pair, rand the resultant laterally-spaced groups, not only provide for the improved stereophonic sound coverage described, but also provide an effectively localized stereophonic sound reproducing center or speaker system that may be enclosed within the desired single cabinet structure or equivalent enclosure means here represented by the rectangular dash Iline enclosure 30. This enclosure means may be of such moderate dimensions as to be adapted for use in the home, and yet maintain the centralized stereophonic loudspeaker system outlined, for providing the full extended and relatively wide stereophonic sound area shown in FIGURE 1. It will be noted that this area extends frontal- 1y of the enclosure means and that the loudspeaker units all face generally in this frontal direction, thereby further adapting the system for use in a single cabinet structure of lgood design as will hereinafter be shown and described.

As referred to hereinbefore, the pair of loudspeaker units L3 and R3 occupy a position corresponding to the rotation of the pair of loudspeaker units L1 and R1 to the left in a counterclockwise direction, and may be retained in this position in place of speaker units L3 and R3, as shown in FIGURE 2, to which attention is now directed. In FIGURE 2, the enclosure means or cabinet structure 30 thus includes `only two pairs `of spaced speaker units LI and R1, and L2 and R2, the latter occupying the same positions as in the `arrangement of FIGURE l. The enclosure means is positioned in the room area outlined by the walls 14, 15, 16 and 17, Iand provides a frontal area of lgood auditory perspective comprising the same three zones 20, 24 and 26 with substantially the same degree of uniformity. For commercial use, and in the interest `of cost reduction and size requirements for the enclosure means, two pairs of speaker units as shown in FIGURE 2, are often desirable, and commercial forms :of la unitary speaker system of this type will hereafter be shown and described.

In FIGURE 2, the stereophonic left-hand sound zone or area 24 is covered by the vspeaker units L2 and R2 as a stereophonic pair connected with the supply lines 18 and 19 las before. Likewise the right-hand sound zone or area -26 is covered by the speaker units L1 and R1 which now replace the units L3 and R3 of FIGURE l. The middle or center sound zone 20, between the zone boundary lines 21 and 22, is covered stereophonically by the loudspeaker units L1 and R2 in this arrangement, and the three areas `or zones are found to merge into an area of good auditory perspective in depth and width to include the sidewall areas as shown, between the boundary lines 25 and 27, as in the case of AFIGURE 1. The speaker units L1 and R1 are connected respectively with the channel input circuits I8 and 19, as in the system of FIGURE 1, for receiving stereophonic signals in unison with the units L2 and R2.

Refer-ring now to FIGURES 3 and 4, along with FIG- URE l, a practical embodiment of the stereophonic loudspeaker system of FIGURE y1 yis shown which provides proper clearance for the delivery of sound in a frontal direction fromeach speaker unit without interference with the others. For this purpose, the loudspeaker units may be located at different elevational levels in the enclosure means 30, which is shown as a rectangular cabinet structure. The enclosure means may be rnade to have a moderate height sutiicient to accommodate as many las three tiers or levels 32, 33 and 34 for the speaker units, as shown more particularly in FIGURE 3. It will be seen that the unit R2 is located in the upper right-hand front corner of the enclosure means while its companion unit L2 is located in the lower lefthand rear corner of the enclosure means. Likewise the loudspeaker unit L3 is located in the upper left-hand front corner ofthe enclosure means while its companion speaker unit R3 is located in the lower right-hand rear corner of the enclosure means. With this arrangement, the speaker units f L2 and R3 are located in the lowermost tier or level 32 and the speaker units L3 and R2 are located in the uppermost or top tier or level 34. The speaker units L1 and R1 are then located in an intermediate tier or level 33. In FIGURE 4, the three related substantially vertical I l planes, -designated as plane X, plane Y, and plane Z, are

Y shown in relation to the respective pairs of loudspeakers toV which they pertain.

The speaker units are thus positionedto deliver stereophonicfsound with proper phase and intensity factors into the enlanged listening area trontally of the cabinet in accordance with the arrangement shown in FIGURE l. The v loudspeaker system shown has lbeen found to provide eiective stereophonic sound reproduction over an extended -and relatively wide area constituting a major portion of an ordinary room in the unitary enclosure means or cabinet structure as shown, with moderate dimensions of less than y5 feet in width, 3 feet in height, and 2 feet in depth.

In the stereophonic loudspeaker system shown in FIG- URES 3 and 4, like speaker units are provided, and are connected, :as shown in FIGURE 4, to the stereophonic l input circuit and kprovide Vsubstantially uniform sound distribution when arranged in similar angular positions as to the frontal area or enclosure means in accordance with the principles described and shown in connection with the system of FIGURE 1.

It should be noted that, as shown in FIGURE 4, the respective planes X and Z -for the angled loudspeaker pairs, L3-R3 and LI-Rl, are always at an acute angle and less than 90 to the frontal plane of the enclosure means or cabinet structure, or to the axis of said enclosure means or cabinet structure. This arrangement has been found to provide eiectlve wide-area frontal stereophonic sound coverage, without too greatly increasing the depth `of the cabinet struct-ure as a suitable `furniture item for lionne use.

It will be noted that the units of each pair of loudspeakers are spaced apart in stereophonic relation in the end sections 36 and 37 of thecabinet structure or enclosure means,`\and which are referred to in FIGURE 3 It will be noted that the speaker units in 'each end section are provided with individual baiile means 45, as indicated .more clearly in FIGURE 3, facing in diiercnt ifrontal directions, with the baffle means for each pair of speaker units in substantially the same generally vertical plane. This relation, yas hereinbefore referred to, is shown more clearly in FIGURE 4 with reference to the planes X, Y and Z. |Each related pair of speaker units is thereby v.faced for directing reproduced sound therefrom in complementary relation with the other related pairs of speaker Y units according to the `diagram shown in FIGURE l.

A further embodiment of the invention as constructed in accordance with the arrangement of FIGURE l, is shown in FIGURES 5 and `6, `as a'modication in the placement and elevational relation ot the loudspeaker units shown in, FIGURES 3 and 4. Referring to- FIGURES 5 and 6, Ithe unitary enclosure means 30 is la similar rectangular cabinet structure provided with spaced left and right speaker sections 35 and 37 at the lleft and right hand endsthereof, with a central apparatus section 38 therebetween. In the interests of height reduction of the 'cabinet structure, only the upper two'levels or tiers 33 and as the leftspeaker section and the rightspeaker section,

respectively. These sections are separated by `a central apparatus section 33,Y outlined in FIGURE 3 by dotted lines 39 and 4d and by speaker confining walls 42 and 43 extending from front to rear and Ifrom top to bottom of the'cabinet structure internally thereof, 4as shown in FIGUREA.

Within the space thus effectively provided between the speaker sections, associated stereophonic sound reproducing apparatus and equipment may be mounted for use l in connection with the loudspeaker system, without increasing the size ot Vthestructure beyond that required Vlor the production ot `the stereophonic sound, and without the use of any additional enclosure cabinet means there- `for. This arrangement is a distinct advantage in the constructionof radio, phonograph and like stereophonic sound reproducing equipment tor homeuse in the entertainment field, as the entire stereophonic sound reproducing system may thenbe enclosed in a unitary cabinet structure of moderate dimensions adapted tor blending with the decor of an average living room or the like, andv the requirement for external cable or wire'connections to spacedV -cabinet units is obviated. p

34 are'provided, Vand the pair of loudspeaker units L2 'and R3 are located in the upper tier 34 yalong with the speaker units vL3 and R2. Thus, as will be seen from an inspection of FIGURES 5 and 6, the diagonally '.Eacing pairs of speaker units L2' and R2, vand L3 and R3 are in the same upper level or tier 3d, whereas the Ifrontally facing a pair of speakerunits Ll and RI are in the same level or tier as in the preceding embodiment.

As will be seen from the baille arrangement in IFIGURE 6, in order to provide two pairs of speaker units in thek same level or tier, the related pairs of speakers are retained-in substantially the same planar arrangement as in the embodiment of FIGURES 3 Iand 4 without increasing the enclosure depth, strom 'front to rear, and are similarly connected to Ithe left and right-channel inputV circuits 18 and I9, whereby they operate in substantially the same manner `as described for the embodiment of FIGURES 3 and 4. The advantage in this construction Y is the considerable reduction in the height of the enclosure means or -cabinet str-ucture that is provided thereby with three pairs of speaker units. k

It will `also be noted that in this embodiment of the invention, an additional small high-frequency loudspeaker unit .is associated in each bale means 45 with `the main loudspeaker unit of each pair as shown in FIGURE 5. vThe showing of these additional units in FIGURE 6 would reduce the clarity with which the bafile means for the speaker units is shown, and hence has been omitted. The high-frequency units are designated with the same reference characters as the main speaker units, with the sub let-ter a added, `as appears in FIGURE 5.

The total number of 'speaker units and their speaker connections, however, are shown completely in FIGURE 7, to .which attention is `directed along with FIGURES 5 kan-d 6. It will be seen that in the left speaker section 36, Vthe main speaker urn'ts, LI, L2 and L3, are serially connected directly with the left channel input circuit 18.'

Ythe main speaker units through a frequency-discriminating coupling capacitor 5l. The coupling capacitors 50 andi, asis Well understood, prevents or limits the application of sound signal currents inthe lower frequency ranges from being applied tothe high-frequency units.

Referring to FIGURES 8 and 9, along with FIGURE 2, a further practical embodiment of the stereophonic loudspeaker system of the present invention is provided in a two-level speaker arrangement similar to that of FIG- URES .and 6, but in which only two stereophonic pairs of speaker units, Ll--Rl and L2-R2, are used for coverage of the stereophonic sound area, in accordance with the system of FIGURE 2. As in the preceding embodiment, the loudspeaker units are located at two diilerent elevational -levels Iin the enclosure means 30, =wl1ich is a similar rectangular cabinet structure having two speaker tiers or levels 33 and 34, whereby the enclosure means may have a moderate height.

The two pairs of speaker units are located in positions corresponding to those shown in FIGURE 2, Iwith unit R2 in the upper right-hand corner of the enclosure means while its companion unit L2 is located the lower lefthand rear corner of the enclosure means, to cover a frontal sound distribution area to the -left of the center line or axis of the enclosure means. Likewise the loudspeaker unit Ll is located in the upper left-hand `front corner ofthe enclosure means, while its companion speaker Aunit Rl is located in the lower right-hand rear corner of the enclosure means, to cover a fron-tal sound distribution area to the right of the center line or axis of the enclosure means. The speaker units are connected with the stereophonic channel input circuits 1S and 19, as shown in FIGURE 9, in the same vleft and right-hand groups and for the same purpose as explained in the connection with FIGURE 2. vPreferably like units are provided, as indicated in the dra-wing.

It will be noted that in this embodiment, the baille means 45 for the lower level speaker units, R1 and L2, are slightly tilted or tipped upwardly by a relatively small angle to compensate for the lower level of these speaker units with respect to their companion units L1 and R2 respectively, in each pair, in lling the volume or sound area lfrontally more eifectively in accordance with the diagram shown in FIGURE 2, and as explained in connection therewith.

The respective planes, X and Z, for the angled loudspeaker pairs, Ll-Rl and L2-R2, are at an acute angle and less than 90 to the frontal plane, or to the axis, of the enclosure means or cabinet structure Sil. This arrangement, with two pairs of speaker units, has been found to provide effectively wide-area frontal stereophonic sound coverage, with a cabinet structure of moderate dimensions in depth front-to-rear. As in the preceding embodiments, it will be noted that the units of each pair of loudspeaker units are spaced apart in stereophonic relation in the end sections 36 and 37 of the cabinet structure or enclosure means, and that these sections are separated by a central section 38, outlined in FIGURE 8 by the dotted lines 39 and 40. Thus it will be seen that the two tier or two-level construction, while providing slightly less vertical height, may likewise provide for the mounting and housing of associated stereophonic sound and reproducing equipment, as in the preceding embodiments.

The stereophonic loudspeaker system embodying the invention, as constructed according to the arrangement of FIGURE 2 and as shown in FIGURES 8 and 9, in a practical embodiment thereof may be modified further for commercial use, to provide a complete stereophonic sound reproducing system, with associated stereophonic radio and phonograph apparatus, in a unitary cabinet structure or enclosure means, as shown in FIGURES 10 and l1, to which attention is now directed.

In this commercial modification, a single elongated or relatively-wide rectangular cabinet 55, which may be of any suitable period design, is provided as a unitary enclosure means for a complete stereophonic radio-phonograph sound reproducing system. 'Ihis system provides two pairs of main stereophonically related speaker units L1 and R1, and L2 and R2, in left and right-hand end l@ sections 56 and 57 of the cabinet, and radio, signalamplifying, and phonograph record-changer apparatus 1n a central apparatus section 53.

In the present embodiment, the speaker units L1 and R2 are located in the upper level and mounted in enlarged angular baille means 59 and 6i?, respectively. The speaker units L2 and Rl are located in the lower level in enlarged angular baille means 6l and 62, respectively, in substantially the same relation as in the embodiment of FIGURES 8 and 9. For wide-range high-fidelity reproduction of sound in a radio-phonograph system, each of the main speaker units, L1, L2, R1, and R2, is provided with an associated small high frequency unit Lla, L2a, Rla, and R2a, respectively, mounted in the same baille means therewith as shown. The baille means 59 and 62 are faced in a frontal direction and slightly to the right with respect to the center line or axis of the enclosure means, as in FIGURE 9 for example, and likewise the baille means 60 and 6l face in a frontal direction and slightly to the left with respect to the center line or axis of the enclosure means, in the planar relation shown in FIGURE 9 for example, thereby to provide directional sound distribution in accordance with the system of FIGURE 2.

The central apparatus section 58 includes FM radio receiver means 63 and AM receiver means 64 mounted behind a front panel 65 in which are located the usual control knobs 66 and like elements for operating the system. Below the radio panel 65, in the central apparatus section 58, is a stereophonic phonograph record changer 67 mounted in a sliding drawer 68.

In the circuit of FIGURE ll, the main speaker units Rl and R2, in the right speaker section 57, are connected in parallel relation to the right channel input circuit 19, the speaker unit R2 being connected through a coupling capacitor 70 for slightly limiting the bass response, since the speaker unit R2 is of slightly smaller size than the corresponding right channel lower speaker unit R1, to conform to the limited space in a cabinet design relatively restricted in depth. The two high-frequency speaker units R2a and Rla in the right speaker section are connected in parallel relation to each other and connected to the input circuit 19 through a coupling capacitor 71 for limiting the ilow of low-frequency current thereto, as explained hereinbefore for the modification shown in FIGURES 5, 6 and 7.

Likewise, in the left speaker section 56, the main speaker units Lll and L2 are connected in parallel relation to the left channel input circuit 18, the smaller speaker unit L1 having a coupling capacitor 72 in series therewith to slightly limit the bass response. The two high-frequency units Lila and L2a are connected in parallel and are connected to the input circuit I8 through a coupling capacitor 73 for limiting the ilow of low-frequency current thereto.

The loudspeaker units in each end section are therefore connected together, in this case in parallel, for operation as the left and right-channel sound reproducing elements of a two-channel stereophonic radio-phonograph sound reproducing system. The loudspeaker system has two signal input circuits so that the pairs of loudspeaker units Ll-Rl, and L2-R2, and their associated high frequency units, are connected for stereophonic operation in unison response to the applied two-channel stereophonically-related sound signals from separate channel ampliiiers for the system.

All the speaker units are supplied with amplified sound or audio-frequency signals through left and right-channel ampliilers 75 and 76, which are connected, respectively, with the input circuits 18 and I9 for delivering ampliiled two-channel stereophonic sound signals to the speaker systern. The channel ampliilers, which may be referred to as channel A and channel B ampliilers, are connected through suitable audio frequency control circuits 78, and a selector switch 79, to different sources of stereophonic signal supply, such as the receivers 63 and 64 or the record changera? The stereophonic channelY A and channel B output circuits, for the record'changer are indicated at Sl and 82 respectively, while-the stereophonic output circuits for the receivermeans are indicated at 83 and 84, respectively, for channels A and B.

The selector switch is indicated as being in a position to connect the record changer to the channel amplifiers 'l5 and 76 through the control circuits 78,for stereophonic record reproduction. As is understood, the audio control circuits 73 may include volume orA gain-control means, treble, and bass control means, as well as a channel balance means, operable by certain of the panel mounted control knobs 66.` No further description of these circuits need be given as they do not form part .of

the present invention, and are known and well understood.

- When the selector switch '79 is turned to connect the radio receiver means to the channel amplifiers through yor like loudspeaker units, the units of each pair being n spaced apart at opposite ends or sides of the cabinet structure in separate sections and arranged in the same or different tiersY or levels. In a stereophonic sound reproducing loudspeaker system involving two pairs of speaker units as in the present example, the units of each pair are at different levels and effectively at diagonally t opposite cornersof the cabinet structure when the latter is of rectangular configuration. This arrangement has `been found to give greatly improved stereophonic soundY distribution. However, the speaker units of each pair may be at the same level, as hereinbefore shown and described, in a vtwo-level cabinet structure `or like enclosure means. l

In the present embodiment of FIGURE l; as in the others, the speaker units in eachV end section are provided with individual baffle means facing in different generally frontal directions, the'baflie means for each related pairV of speaker units being in substantially the same generally vertical plane and faced for directing reproduced sound therefrom in complementary relation with the other related pairs of speaker units, to provide stereophonic sound reproduction with improved audio perspective over the relatively wide area frontally of the enclosure means or cabinet structure. Y f Y The radio-phonograph stereophonic sound reproducing system shown in the present embodiment is representative of a sound reproducing system of a type suitable for use in the home entertainment iield. From a considerationk of this embodiment however, it will be seen that the rsingle-unitV stereophonic loudspeaker system of the present y invention |notonly provides for effective stereophonic sound distribution, buty also provides effective means for housing associated stereophonic sound reproducing equipment or apparatus, such as radio, phonograph and like apparatus, as a distinct advantage in the home entertainment field. The unitary loudspeaker enclosure means may be made sufficiently wide, without exceeding the l2 lated orV separable, if desired, for easier manufacture and/ or transportation.

With this system there are no separated space requirements for the installation and fitting yof a multiplicity of units to a decor of a room. Instead, a unitized cabinet structure or like enclosure means provides housing and bafie means for an entire stereophonic sound reproducing system which can provide stereophonic sound with good auditory perspective over the full width and depth of a desired stereophonic sound area.

What is claimed is: t

V1. A unitary stereophonic loudspeaker system for the reproduction ofy sound in auditory perspective, comprising in combination, unitary speaker enclosure means havlimits of moderate dimensions, to provide for this asso- Y iciated equipment in the central section or area, which thereby improves the spacing between the end sections containing the loudspeaker units. This construc-tion therefore avoids the need for any apparatus cabinet orY enclosure means in a stereophonic sound reproducing system. However, the sections may be made to be articuing a frontal and two spaced side areas, aplurality of speaker units mounted in and baffled by said enclosure means in stereophonically-related pairs, one speaker unit of each pair being positioned in `one of said side areas and the other speaker unit of each pair being positioned inthe other of said side areas, said speaker pairs being mounted in different generally vertical planes and facing in different generally frontal directions to provide distribution of reproduced stereophonic sound therefrom in lateral directions and in depth over an extended area frontally of said enclosure means from effectively a common centralized location, and input circuit means connecting said related pairs of speaker units for response to two stereophonically-related sound signals.

2. A stereophonic loudspeaker system for` the reproduction of sound in auditory perspective, comprising in combination, a sectionalized cabinet structure having two end 'sections providing laterally-spaced loudspeaker enclosure and baffle means, a plurality of loudspeaker units mounted inV said end sections in different intersecting common planes in pairs to face the front of said structure,

and means connecting said loudspeaker units electrically for stereophonic sound reproduction in' response to applied stereophonically-related sound signals.

' 3. A stereophonic loudspeaker system for the reproduction of sound in auditory perspective, comprising in `combination, av sectionalized cabinet structure having two end sections providing laterally-spaced loudspeaker enclosure and baffle means and having an axis extending between said end sections, a plurality of loudspeaker units mounted in said end sections in different common planes in pairs to face frontally at different acute angles with respect to the axis of the structure into a relatively wide stereophonic sound area from effectively a common centralized location, whereby each pair of loudspeaker units covers a predetermined zone of said stereophonic sound area, and means for electrically connecting thek loudspeaker units in each end section together for the application thereto of one of a pair of stereophonically-related sound signals. p

4. A stereophonic loudspeaker system for the reproduction of sound in lauditory perspective, comprising in combination, a sectionalized cabinet structure having twoY end sections providing laterally-spaced loudspeaker enclosure and baffle rneans, a plurality of like loudspeaker units mounted in said lend sections in different intersecting common planes in pairs to face the fron-t of said structure, said loudspeaker units being thereby spaced in depth :from front to rear of said cabinet structure, the loud speaker units of at least two of said pairs further beingrmounted at different elevational ilevels, and means connecting said loudspeaker units electrically for stereophonic sound reproduction in response to applied stereophonically-related sound signals.

5.y A stereophonic sound-reproducing loudspeaker systern, comprising `in combination, ta cabinet structure for enclosing stereophonic sound reproducing means, a plurality of `loudspeaker units with vindividual baffle means for each unit facing in different generally frontal directions in related pairs for effective sound distribution f i3 therefrom in auditory perspective, the loud speaker units and bailie means lfor each pair being spaced apart and located in the end areas of said cabinet structure, and circuit means connecting said loudspeaker units in said related pairs for the application thereto of two stereophically-nelated sound signals.

6. A unitary stereophonic sound-reproducing loudspeaker system, comprising in combination, a longitudinally extending cabinet structure for enclosing stereophonic sound reproducing means, a ir-st pair of longitudinallyspaced-apart left and right loudspeaker units each mounted in said cabinet structure to face in a first genenally frontal direction and a second pair o-f longitudinally spaced-apart left and Aright loudspeaker units each mounted in said cabinet structure to face in a second and different generally frontal direction from said first pair, the left speaker-s of each pair adapted to be connected to reproduce one of a pair of stereophonically-relatedsignals, and the right speakers of each pair adapa-ted to be connected to reproduce the other f said pair of stere- .ophonically-related signals.

7. A unitary stereophonic loudspeaker system for twochannel stereophonic sound reproduction comprising, a single cabinet structure providing la central section and two relatively -wlidely spaced right land left-hand end sections, a plurality of sound-reproducing speaker units mounted in said end sections in stereophonically-related pairs, being thereby-spaced in Width from side to side of said structure, and said pairs of speaker units facing (frontally in different generally vertical planes, thereby to provide an enlarged stereophonic sound area having improved .auditory perspective and uniform frequency characteristic frontally of said structure in response to applied stereophonically-related sound signals, and two-channel signal-input circuit means connecting the speaker units in each end section of said structure Ifor applying said stereophonically-related sound signals thereto.

.8. A unitary loudspeaker system for stereophonic sound reproduction comprising, a single speaker cabinet, a plurality of like sound reproducing speaker units mounted therein spaced in depth from front to rear and spaced in width from side to side of said cabinet and facing frontally in like stereophonically-related pairs in different generally-Vertical planes, thereby to provide an enlarged stereophonic sound rarea frontally of the cabinet having improved sound Aand frequency distribution with a high degree of auditory perspective in response to applied stereophonically-related sound signals, and input circuit means connecting said related pairs of speaker units for response in unison to two stereophonicallyrelated sound signals.

9. A unitary `loudspeaker system for stereophonic sound reproduction comprising, a relatively Wide cabinet structure providing a central apparatus enclosure section and tWo end sections in spaced relation, said sections having substantially a common frontal plane, a plurality of like sound-reproducing loudspeaker units mounted in each of the end sections and facing said frontal plane at different acute angles in complementary pairs, one unit of each pair in each end section, thereby to provide an enlarged stereophonic sound area having a high degree of auditory perspective frontally of the cabinet structure, and means electrically connecting the loudspeaker units in each end area together for two-channel stereophonic operation in response to applied stereophonically-related sound signals.

10. A unitary stereophonic sound reproducing system comprising in combination, a relatively-Wide apparatus cabinet providing a substantially centnal enclosure area for stereophonic sound-signal translating apparatus and two end enclosure tareas :for associated stereophonic loudspeaker means in spaced nelation to each other on opposite sides of said Iapparatus enclosure area, at least two pairs of like sound-reproducing loudspeaker units, the units of each pair being spaced apart one in each of said end enclosure areas, the speaker units in each end enclosure area having individual baffle means facing in different generally frontal directions in related pairs for directing reproduced sound therefrom in improved auditory perspective and frequency distribution over a relatively wide area frontally of said cabinet, and means for applying a rst' signal substantially identically to the loudspeaker units in one end enclosure area and applying a second signal substantially identically to the loudspeaker units in the other of said end enclosure areas, said firs-t and second signals being stereophonically related.

11. In a unitary stereophonic sound reproducing system,

f comprising in combination, an apparatus cabinet providing a substantially-central apparatus-enclosure section and two right and left-hand loudspeaker-enclosure sections in spaced relation to each other on opposite sides of said apparatus-enclosure section, two pairs of sound-reproducing loudspeaker units, the units of each pair being spaced vapart one in each of said end sections and relatively spaced in depth from front to rear of said apparatus cabinet, the speaker units in each end section having individual bathe means facing in different generally frontal directions, the baffle means for each related pair of speakerunits being in substantially the same generallyvertical plane and faced for directing reproduced sound therefrom in complementary relation to other related pairs of speaker units, thereby to provide stereophonic sound reproduction with improved auditory perspective over a relatively wide area frontally of said cabinet, and means for electrically connecting said pairs of loudspeaker units for stereophonic operation in uni-son in response to applied stereophonically-related sound signals.

12. A unitized stereophonic loudspeaker system comprising, in combination, cabinet structure with spaced right and left-hand end sections, a plurality of like speaker units mounted in cach of said end sections to face in different generally frontal directions in related pairs with respect to said cabinet structure, said speaker units being located in said end sections at different elevational levels and at different depths within the structure to provide substantially-duplicate pairs of spaced speaker units, one unit of each pair in each end section, for sound reproduction in substantially uniform auditory perspective over a relatively large area frontally of said structure in response to applied stereophonically-related sound signals, and means providing an input circuit connecting the speaker units in each end section for the substantially identical application thereto of one of said sound signals.

13. In a unitized stereophonic loudspeaker system comprising in combination, a single apparatus cabinet structure having right and left-hand loudspeaker-enclosing end sections, at least two loudspeaker units mounted in each of .said end sections at different higher and lower elevational levels and facing in different generally frontal directions, the loudspeaker units lin one end section being stereophonically paired each with a loudspeaker unit in the other end section and positioned therewith to face substantially in the same frontal direction, thereby to provide stereophonic pains of loudspeaker units facing in different generally frontal directions to provide stereophonic sound distribution frontally over an enlarged area with a high degree of auditory perspective, and input circuit means for electrically connecting the loudspeaker units in each end section together for the application thereto of one of a pair of stereophonically-related sound signals.

I14. A unitized stereophonic loudspeaker system as defined in claim 13, wherein the loudspeaker units mounted at the lower elevational level are tilted upwardly by a relatively small angle to compensate for the lower level position thereof in providing said stereophonic sound distribution.

15. A unitized stereophonic loudspeaker system for use with stereophonic sound reproducing apparatus, comprising in combination, an apparatus cabinet structure and two adjoining right and left-hand loudspeaker-enclosing end sections on either side thereof, at least two loudspeaker units mounted in each of said end sections at different elevational levels andfacing in different angular direction-s frontally, a rst loudspeaker unit in onerend section being stereophonically paired with a vrst loudspeaker unit in the other endsection, a second loudspeaker unit in said one end section being stereophonically paired with a second loudspeaker unit in said other end section, thereby to provide stereophonic pairs of loudspeaker units facing in different frontal directions to provide uniform sounddistribution frontally in auditory perspective, and means for electricallyk connecting the loudspeaker units Yin each end section together for the application thereto of one of a pair of stereophonically-related sound signals.

16. A unitized stereophonic loudspeaker system for use with stereophonic -sound reproducing apparatus, comprising in combination, a cabinet structure having a generally rectangular configuration providing top, frontaland side areas-with a substantially-central apparatus section and two adjoining end sections on either side thereof, at

least two loudspeaker units mounted in each of said end sections at different elevational levels and facing in dif ferent angular directions toward said frontal area, a rst loudspeaker unit in one end section stereophonically paired with a first loudspeaker unit inthe other end section and positioned therewith substantially in a common plane having a generally'vertical disposition and an angle of .less than 90 with respectto said frontal area, a second loudspeaker unit in said one end section stereophonically paired with ya second loudspeaker unit in said other end section and positioned therewith substantially in a second and different common plane having va generally vertical s '.15 Y disposition and an Yangle of less than 90 with respect to said frontal area in complementary relation toisaid plane, thereby to provide stereophonic pairs of loudspeaker units facing in different frontal directions to provide substantially uniform sound distribution frontally in auditory perspective, and means for electrically connecting the loudspeaker units in each end section together for the applica-k tion thereto of one of a'pair of stereophonically-related sound signals.

117. A sound reproducing system comprising a cabinet enclosure, a rst pair of loudspeakers mounted respectively Yin opposite ends of said cabinet and aligned to face in the same direction, a second pair of loudspeakers mounted respectively in opposite ends of said cabinet and aligned to face in the same direction, ysaid first pair of said loudspeakers facing to the right of the frontally facing direci v tion of said enclosure andsaid second pair of speakers facing to the leftV of the frontally facing direction of said enclosure, and terminal means for applying one of a pair of stereophonically related sound signals to` the loudspeakers in one endof said cabinet and the other of said pair of stereophonically related sound signals kto the loudspeakers in the other end of said cabinet.

kReferences Cited ini-the le of this patent UNITED' STATES PALENTSV 1,199,441 France V June 22, 

1. A UNITARY STEREOPHONIC LOUDSPEAKER SYSTEM FOR THE REPRODUCTION OF SOUND IN AUDITORY PRESPECTIVE, COMPRISING IN COMBINATION, UNITARY SPEAKER ENCLOSURE MEANS HAVING A FRONTAL AND TWO SPACED SIDE AREAS, A PLURALITY OF SPEAKER UNITS MOUNTED IN AND BAFFLED BY SAID ENCLOSURE MEANS IN STEREOPHONICALLY-RELATED PAIRS, ONE SPEAKER UNIT OF EACH PAIR BEING POSITIONED IN ONE OF SAID SIDE AREAS AND THE OTHER SPEAKER UNIT OF EACH PAIR BEING POSITIONED IN THE OTHER OF SAID SIDE AREAS, SAID SPEAKER PAIRS BEING MOUNTED IN DIFFERENT GENERALLY VERTICAL PLANES AND FACING IN DIFFERENT GENERALLY FRONTAL DIRECTIONS TO PROVIDE DISTRIBUTION OF REPRODUCED STEREOPHONIC SOUND THEREFROM IN LATERAL DIRECTIONS AND IN DEPTH OVER AN EXTENDED AREA FRONTALLY OF SAID ENCLOSURE MEANS FROM EFFECTIVELY A COMMON CENTRALIZED LOCATION, AND INPUT CIRCUIT MEANS CONNECTING SAID RELATED PAIRS OF SPEAKER UNITS FOR RESPONSE TO TWO STEREOPHONICALLY-RELATED SOUND SIGNALS. 